The present invention relates to improvements in vibration damping apparatus (also known as oscillation dampers) which can be utilized with advantage in the power trains of motor vehicles, for example, between the internal combustion engine and/or another prime mover and the change-speed transmission and/or another driven unit of the power train.
A vibration damping apparatus normally comprises input and output members (e.g., shafts) which are rotatable with and relative to each other about a common axis, and one or more energy storing elements (such as coil springs, diaphragm springs or the like) which yieldably oppose rotation of the input and output members relative to each other. Depending, for example, on the nature of the motor vehicle, the arrangement can be such that the input and output members of the vibration damping apparatus have limited or unlimited freedom of angular movement relative to each other. Furthermore, the resistance which the energy storing element(s) offers or offer to rotation of the input and output members relative to each other can remain substantially constant or varies, either gradually or stepwise, depending on the magnitude of fluctuations of torque which is to be transmitted from the input member to the output member under normal operational circumstances (when the engine drives the wheels of a motor vehicle), or under other than normal circumstances (e.g., when the vehicle is coasting).
Adequate damping of vibrations is desirable on the additional ground that it contributes significantly to the comfort of the occupant or occupants of a motor vehicle.
An object of the instant invention is to provide a vibration damping apparatus which can furnish an optimal or at least highly satisfactory vibrations damping action under normal circumstances of use as well as under certain exceptional circumstances, e.g., irrespective of fluctuations of RPM of the rotary output member of a prime mover, such as the rotary crankshaft or camshaft of an internal combustion engine in the power train of a motor vehicle.
Another object of the invention is to provide an apparatus which can reliably filter oscillatory movements between the driving and driven constituents of a power train.
A further object of the invention is to provide a novel and improved torque transmitting connection between a prime mover and a driven unit, e.g., between the prime mover and the transmission (such as a continuously variable transmission known as CVT) in the power train of a motor vehicle.
An additional object of the invention is to provide a vibration damping apparatus the characteristics of which can be readily selected or altered to carry out the required damping action in dependency upon the intended use of the apparatus and/or of the power train in which the apparatus is being put to use.
Still another object of the invention is to provide a simple and inexpensive but highly versatile vibration damping apparatus the useful life of which at least matches those of presently known and utilized vibration damping apparatus.
A further object of the invention is to provide a power train which employs one or more torsional vibration damping apparatus of the above outlined character.
The invention is embodied in a vibration damping apparatus which comprises an input member (e.g., a fly-wheel) which is rotatable about a predetermined axis and includes components (e.g., discs made of sheet metal) defining an annular chamber, an output member which is rotatable about the predetermined axis with and relative to the input member, and a damper assembly which is arranged to yieldably oppose rotation of the input and output members relative to each other and includes energy storing elements which are at least partially confined in the annular chamber (e.g., one, two or more of several energy storing elements can be fully or partially received in the annular chamber). The chamber has a sealed radially outer portion and is at least partially filled with a supply of a suitable viscous fluid. A radially inner portion of the output member comprises or constitutes a hub which is connectable with and is arranged to transmit torque to and receive torque from a rotary part of a power train. The damper assembly further comprises a rotary annular output element which is arranged to transmit torque between the input member and the hub and has at least some freedom of rotation relative to the input member against the opposition of at least some of the energy storing elements.
The rotary part of the power train can include a shaft which is non-rotatably receivable in the hub and can constitute the input shaft of a suitable transmission, e.g., an infinitely variable-speed transmission known as CVT.
The apparatus can further comprise means (e.g., an annular array of bolts and/or other suitable fasteners) for preferably separably affixing the input member to a rotary output part of a prime mover in a motor vehicle including the power train; the output part can constitute or include the crankshaft or camshaft of the internal combustion engine in a motor vehicle.
The aforementioned components of the input member can include two dished or cupped parts having radially outer portions which are remote from the predetermined axis and are sealingly secured to each other. As a rule, the components are or can constitute ring-shaped parts at least one of which is dished or cup-shaped. Such parts have neighboring radially outer portions which are remote from the predetermined axis, and the input member comprising such components can further include a circumferentially complete welded seam which sealingly connects the radially outer portions of the ring-shaped parts to each other to thus prevent escape of viscous fluid from the annular chamber radially outwardly beyond the radially outer portions of the ring-shaped parts.
At least one of the two components forming part of the input member can consist (entirely or in part) of a suitable metallic sheet material.
It is presently preferred to employ a viscous fluid which is a lubricant (e.g., a grease or another suitable high-viscosity fluid).
The annular chamber can be configurated in such a way that it includes a plurality of sections each of which receives at least one energy storing element. The input member which defines such chamber is preferably provided with abutments which alternate with the arcuate sections of the annular chamber (as seen circumferentially of the chamber) and contact the energy storing elements in the neighboring sections of the chamber. For example, the annular chamber can include at least two arcuate sections having identical or similar radii of curvature. The energy storing elements in the sections of the annular chamber can include at least two arcuate energy storing elements with radii of curvature which at least approximate each other.
It is often preferred to design the annular chamber in such a way that it includes fewer than five arcuate sections each of which extends along an arc of between 60% and 96% of 360xc2x0/n (wherein n is the number of sections). Each energy storing element can comprise a single spring or a plurality of springs (e.g., two interfitted coil springs). The energy storing elements in the arcuate sections of the annular chamber can constitute arcuate energy storing elements having centers of curvature at least close to the predetermined axis; the energy storing elements in the sections of the annular chamber can extend along arcs of between 60% and 98% of 360xc2x0/n wherein n is the number of arcuate energy storing elements.
If the annular chamber is a circumferentially complete annular chamber, it is often preferred to select the dimensions of the energy storing elements in such a way that they occupy between about 60% and 95% of the chamber (as seen in the the circumferential direction of the input member).
Each energy storing element can comprise at least one coil spring. It is often preferred to select and assemble and install the energy storing elements in such a way that at least one of these elements comprises a plurality of coil springs which operate in series; the coil springs of such plurality can include at least two springs having different stiffnesses. Furthermore, at least one of the energy storing elements can include a plurality of interfitted coil springs which may but need not have identical lengths.
The arrangement can be such that the annular chamber has a first radius of curvature and at least one of the energy storing elements has a second radius of curvature which matches or at least approximates the first radius of curvature.
One component of the input member can be constructed and dimensioned and designed in such a way that it includes a radially outer portion remote from and a radially inner portion nearer to the predetermined axis. The radially inner portion can be provided with openings for the aforementioned fasteners which are arranged to connect the one component (i.e., the input member) to a rotary output part of a prime mover, and the aforementioned rotary annular output element of the apparatus can be provided with windows which afford access to a tool (such as a screwdriver or a wrench) for manipulation of the fasteners for the purpose of attaching the input member to the output part of the prime mover, to tighten the fasteners, or to detach the input member from the prime mover.
The one component can constitute a dished component, and the fasteners can constitute threaded fasteners having (a) shanks extending through the respective openings of the one component when the latter is connected to the output part of the prime mover and (b) heads which are accessible to the tool when the one component is connected to the output part of the prime mover.
The apparatus can further comprise a gear (e.g., a large-diameter starter gear) which is affixed to the input member. Alternatively, or in addition to the gear, the input member can be provided with or can carry a suitable pulse generating device; the latter can serve to transmit impulses for management of the internal combustion engine in the power train of a motor vehicle if the improved apparatus is put to use in such power train.
The input member of the improved apparatus can be designed in such a way that it includes a substantially disc-shaped first component connectable to a rotary output part of a prime mover and having a radially outer portion remote from the predetermined axis, and an annular second component which is connected to the radially outer portion of the first component. The chamber is flanked by the first and second components, and the aforementioned gear can constitute a ring-shaped gear which is carried by the second component of the input member. Such apparatus can further include a ring-shaped carrier which is affixed to the second component and supports the gear, and the carrier can comprise a tubular portion which is at least substantially coaxial with the input member and supports the gear. At least some of the energy storing elements can be disposed at a first radial distance from the predetermined axis, and the carrier can constitute a ring which is located at a second radial distance from the predetermined axis; the second distance can match or at least approximate the first distance.
An arcuate internal surface of the input member bounds the radially outer portion of the annular chamber, and the energy storing elements preferably include arcuate springs which bear against the internal surface of the input member, either permanently or at least under the action of centrifugal force while the input member rotates about the predetermined axis. The outline of the internal surface of the input member is preferably such that the internal surface at least partially conforms to the outlines of radially outermost portions of the arcuate springs.
The input member can further comprise a wear-resistant portion which defines the aforementioned internal surface; such wear resistant portion can include or constitute at least one insert which is carried by at least one component of the input member. The at least one insert can comprise or can consist of sheet steel. The hardness of the insert can exceed the hardness of at least one of the aforementioned components forming part of the input member. The wear-resistant portion or insert can have an arcuate cross-sectional outline in a plane including the predetermined axis; such cross-sectional outline can have an at least substantially constant radius of curvature and can extend along an arc of between about 45xc2x0 and 120xc2x0, for example, along an arc of between about 60xc2x0 and 90xc2x0. For example, the wear-resistant portion of the input member can include or constitute a substantially trough-shaped arcuate insert.
The damper assembly of the improved apparatus can include a first damper having a first set or group of energy storing elements and being located in the radially outer portion of the annular chamber, and a second damper located radially inwardly of the first damper. The first and second dampers can be connected in series with each other. Furthermore, the second damper can be disposed radially inwardly of one (e.g., the second) component of the input member, and such second damper can include a second set or group of energy storing elements. The aforementioned rotary annular output element of such apparatus can be non-rotatably connected with the hub of the output member and can be provided with windows for the energy storing elements of the second set or group. The apparatus can be provided with an annular section which surrounds and is rotatable relative to the rotary annular output element. The annular section extends radially outwardly beyond the second damper and engages the energy storing elements of the first set or group. The annular section of the damper assembly can be provided with arms which alternate with the energy storing elements of the first set or group (as seen in the circumferential direction of the annular chamber). The output member of such apparatus can be provided with two substantially disc-shaped walls which are non-rotatably connected with and flank the rotary annular output element as seen in the direction of the predetermined axis. The walls can be located radially inwardly of the first damper and can be provided with windows for the energy storing elements of the second set or group.
The rotary annular output element includes a radially outer portion which can be provided with first profiled sections, and the aforementioned annular section of the damper assembly has a radially inner portion which can be provided with second profiled sections mating with the first profiled sections with a certain play as seen in the circumferential direction of the rotary annular output element. The first and second profiled sections preferably define variable-capacity compartments for the viscous fluid. Such apparatus can further comprise sealing means (e.g., in the form of ring-shaped washers) which flank the compartments as seen in the direction of the predetermined axis. The aforementioned play can determine the extent of angular movability of constituents of the second damper relative to each other.